Porsche replacement sheet metal: Remove the primer?

[sballard]

I know this seems elementary. I've read on this forum that you should always strip off the "primer" from aftermarket sheet metal. But I bought a genuine Porsche longhood fender (for $$$$) and the primer (or whatever you would call the coating) looks outstanding. It seems a shame to strip this off just to lay down a coat of epoxy primer. Any opinions?

[boba]

Do not remove if you are talking about the e-coat.

It is an electrostatic applied coating.

[mreid]

I would strip it to bare metal simply for piece of mind. I've seen the e-coat flake off and I've seen rust under the e-coat. Plus, you want to use a paint system where the layers are fully compatible.

[boba]

There you have it, definitive opinions, each way.

[sballard]

That's where I am...indecisive and right in the middle! I have to say that the primer on the fender looks VERY good. I am also worried about the compatibility with whatever paint will follow. The rest of the car is getting PPG epoxy primer.

[j911brick]

Is the primer green?

[78SCRSMAN]

Strip, sand and apply epoxy primer... don't be foolish!

[Lukesportsman]

I have seen this argued on other forums with different marques and the answer is always the same, Steve. Just like above, everyone has an opinion but no consensus in the end.

Maybe it depends if your putting on a nice $7k driver paint job or a concourse $15k paint job. I don't know, but be inclined to scuff and apply epoxy primer over the E coat. Many in the restoration field spend big bucks to get their uni-bodies E-coated and here we debate on removing it. Isn't one of the advantages of an epoxy primer is that it helps to lock in the lower coats? Use it to balance out the finishes?

Seems a similar debate as to which is better: Strip back to solid OEM primer or always go for a bare metal respray. Different answers from different people all trying to choose the best and offer the best advise.

[Iciclehead]

Ok, extending the question. I am backdating my '89 with '73 parts (Porsche) which are finished in the same black e-coat. I have tried dry ice blasting on part of the car, they can remove the paint or the paint and or the paint, undercoat and factory applied primer coat selectively.

Now, do I blast everything to bare metal to start over, or do I blast to primer and keep the new parts in their e-coat with perhaps a coat of sealer on top, or to I just remove the paint (colour coat).

I am leaning to just removing the paint, using the existing undercoat, primer and the e-coat on the new parts. I was also planning on grinding off the e-coat at the welds to improve their quality.

Thots?

D.

[timmy2]

http://forums.pelicanparts.com/paint-bodywork-discussion-forum/381243-links-freddie-hernandez-101-series.html
From the paint and bodywork forum.
Ask Freddie!

[MTemp]

In my (somewhat limited) experience all e-coats are not created equal, to paraphrase George Orwell. If we are talking genuine Porsche panels then I do not believe you will get a better result than leaving the existing coating in place. Removing and recoating is just another opportunity to let air and moisture to the steel. However the quality of other aftermarket coatings is noticeably different in most cases - some are just painted - and here stripping and recoating is often merited. For old panels of any state stripping and recoating is vital. I have stripped seemingly near perfect panels only to find rust developing underneath.

.... But it's very much a personal preference as you can see!

[sballard]

All very good comments. I've bought Dansk replacement panels before and I would definitely strip the coating off them as they are obviously lower quality. However, the Porsche fender coating is clearly a cut above. Because I am a DIYer who does this after work, I am not so sure that MY strip and primer would be better than a Porsche e-coat.

[sballard]

The primer is black and pretty thick by appearances.

[getto822000]

I'm in the same boat here and wondering what you ended up doing with the OEM panel prep?

[Brian Cameron]

Not sure what he did, but i bought a panel (Partial front left inner fender) from Restoration Design but manufactured by Dansk, covered with black primer but not galvanized. I had a local plating shop strip off the paint and electroplate the bare metal with zinc for $80 canadian which is about 12 cents US.

The suspension pan and gas task support pan I previously bought were made by Resto design and both were galvanized. Doing some panel replacements due to rust so i wanted everything galvanized like the rest of the original body.